Recombinant Escherichia coli for the biomonitoring of benzene and its derivatives in the air

For protection against environmental deterioration, pollutants should be reduced as much as possible. Therefore, a sensitive detection method for air pollutants is required, particularly for benzene, a compound with mutagenic, teratogenic, and carcinogenic properties. Some microorganisms have a number of enzymes that degrade organic compounds. The genetic information for many of these enzymes is codified in plasmids that usually comprise some elements such as proteins and RNA for their replication, and proteins for cell division control. Some plasmids have been obtained from Pseudomonas putida, a ubiquitous microorganism that is able to degrade biologic and inorganic compounds. P. putida contains the TOL plasmid, responsible for the degradation of benzene and its derivatives. The TOL plasmid has been fused with the gene for firefly luciferase (pTNS316 plasmid) to produce a luminescent bacterium (Escherichia coli HB101), which can be applied to the environmental monitoring of these chemicals. The recombinant E. coli transformed with the plasmid (E. coli HB101-pTNS316) was applied to the environmental biosensing of benzene and its derivatives. Measurement of bacteria-generated photons was done using a color-coded device to estimate quantitatively the pollutant concentration. The expression of luciferase was induced in the presence of aromatic compounds but the E. coli sensitivity has a detection limit: this bacterium dies if the benzene concentration is higher than 0.5 ppm and at this concentration the luminescence decreases so it is impossible to detect. Another limit for this biodevice is that the microorganism, very likely, accumulates the benzene and its derivatives, and therefore it is very important to consider the time of exposure. This biomonitor potentially offers a rapid, inexpensive, and sensitive technique for environmental detection of aromatic pollutant compounds.